Virtualization allows multiplexing of the underlying host machine between different virtual machines. The host computer allocates a certain amount of its resources to each of the virtual machines. Each virtual machine is then able to use the allocated resources to execute applications, including operating systems (referred to as guest operating systems). The software layer providing the virtualization is commonly referred to as a hypervisor and is also known as a virtual machine monitor (VMM), a kernel-based hypervisor or a host operating system. The hypervisor emulates the underlying hardware of the host computer, making the use of the virtual machine transparent to the guest operating system and the user of the computer.
Virtual machines can be provided by a cluster of hosts that share a pool of storage. Some conventional systems develop a dedicated file system under the hypervisor to manage the shared pool of storage. However, unsynchronized access to the storage pool by multiple hosts can destroy data integrity. Storage management can further be complicated when storage space is allocated to the virtual machines in real time. Thus, the dedicated file system needs to address the synchronization problem of storage management.